fix(interactive): Fix the bug in the RexNode to Proto Conversion (#3171)

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## What do these changes do?
For a specific expression, i.e. `a.age-(b.age-1)`, there is an issue
when converting it to a proto structure, resulting in missing
parentheses in the generated proto; it gets converted to
`a.age-b.age-1`. This PR is meant to address the issue.

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## Related issue number

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change? -->

Fixes

interactive_engine/compiler/src/main/java/com/alibaba/graphscope/common/ir/runtime/proto/RexToProtoConverter.java

@@ -149,7 +149,7 @@ private OuterExpression.Expression visitBinaryOperator(RexCall call) {
 
     private boolean needBrace(SqlOperator operator, RexNode operand) {
         return operand instanceof RexCall
-                && ((RexCall) operand).getOperator().getLeftPrec() < operator.getLeftPrec();
+                && ((RexCall) operand).getOperator().getLeftPrec() <= operator.getLeftPrec();
     }
 
     @Override

interactive_engine/compiler/src/test/java/com/alibaba/graphscope/common/ir/runtime/RexToProtoTest.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2020 Alibaba Group Holding Limited.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.alibaba.graphscope.common.ir.runtime;
+
+import com.alibaba.graphscope.common.ir.Utils;
+import com.alibaba.graphscope.common.ir.runtime.proto.RexToProtoConverter;
+import com.alibaba.graphscope.common.ir.tools.GraphBuilder;
+import com.alibaba.graphscope.common.ir.tools.GraphStdOperatorTable;
+import com.alibaba.graphscope.common.ir.tools.config.GraphOpt;
+import com.alibaba.graphscope.common.ir.tools.config.LabelConfig;
+import com.alibaba.graphscope.common.ir.tools.config.SourceConfig;
+import com.alibaba.graphscope.common.utils.FileUtils;
+import com.google.protobuf.util.JsonFormat;
+
+import org.apache.calcite.rex.RexNode;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class RexToProtoTest {
+    // convert expression 'a.age - (1-a.age)' to proto
+    @Test
+    public void test_expression_with_brace() throws Exception {
+        GraphBuilder builder =
+                Utils.mockGraphBuilder()
+                        .source(
+                                new SourceConfig(
+                                        GraphOpt.Source.VERTEX,
+                                        new LabelConfig(false).addLabel("person"),
+                                        "a"));
+
+        RexNode braceExpr =
+                builder.call(
+                        GraphStdOperatorTable.MINUS,
+                        builder.variable("a", "age"),
+                        builder.call(
+                                GraphStdOperatorTable.MINUS,
+                                builder.literal(1),
+                                builder.variable("a", "age")));
+        RexToProtoConverter converter = new RexToProtoConverter(true, false);
+        Assert.assertEquals(
+                FileUtils.readJsonFromResource("proto/expression_with_brace.json"),
+                JsonFormat.printer().print(braceExpr.accept(converter)));
+    }
+}

interactive_engine/compiler/src/test/resources/proto/expression_with_brace.json

@@ -0,0 +1,58 @@
+{
+  "operators": [{
+    "var": {
+      "tag": {
+        "id": 0
+      },
+      "property": {
+        "key": {
+          "name": "age"
+        }
+      },
+      "nodeType": {
+        "dataType": "INT32"
+      }
+    },
+    "nodeType": {
+      "dataType": "INT32"
+    }
+  }, {
+    "arith": "SUB",
+    "nodeType": {
+      "dataType": "INT32"
+    }
+  }, {
+    "brace": "LEFT_BRACE"
+  }, {
+    "const": {
+      "i32": 1
+    },
+    "nodeType": {
+      "dataType": "INT32"
+    }
+  }, {
+    "arith": "SUB",
+    "nodeType": {
+      "dataType": "INT32"
+    }
+  }, {
+    "var": {
+      "tag": {
+        "id": 0
+      },
+      "property": {
+        "key": {
+          "name": "age"
+        }
+      },
+      "nodeType": {
+        "dataType": "INT32"
+      }
+    },
+    "nodeType": {
+      "dataType": "INT32"
+    }
+  }, {
+    "brace": "RIGHT_BRACE"
+  }]
+}